ovsdb-idl: Remove write-only member 'commit_seqno' from ovsdb_idl_txn.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Jarno Rajahalme <jrajahalme@nicira.com>
ovsdb-doc: Document immutable columns.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Justin Pettit <jpettit@nicira.com>
vswitchd: Improve the readability of the E-R diagram.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Justin Pettit <jpettit@nicira.com>